(Meth) acrylates are cured by being irradiated with active energy rays such as ultraviolet rays and electron beams or by being heated, and they are thus used in large quantities as a cross linking component of blended materials such as paints, inks, adhesives, optical lenses, fillers, and molding materials or a reactive diluent component.
Inparticular,polyfunctional (meth) acrylates having three or more (meth) acryloyl groups are used in large quantities as a blending component of hard coat paints since the cured products thereof exhibit high hardness and excellent abrasion resistance.
As such polyfunctional (meth) acrylates, trimethylolpropane tri (meth) acrylate, glycerol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tripentaerythritol octa (meth) acrylate, and the like are known.
These (meth) acrylates are produced by an esterification reaction of the corresponding alcohol with the corresponding (meth) acrylic acid or a transesterification reaction.
In the production of (meth) acrylates by an esterification reaction, sulfuric acid and sulfonic acid such as p-toluenesulfonic acid or methanesulfonic acid are used as a catalyst. However, it is required to conduct extraction and washing with an aqueous alkali solution in order to remove the sulfonic acid from the reaction crude product obtained after completion of the esterification reaction, and the step is complicated and the productivity remarkably decreases. In addition, there is a problem that the yield decreases by saponification of a part of the target (meth) acrylate in the extraction operation.
Meanwhile, in the production of (meth) acrylates by a transesterification reaction, the reaction can also proceed without using sulfonic acid. For example, a method in which an organotin compound is used as a catalyst (see Patent Literature 1), a method in which a zinc compound and an organophosphorus compound are concurrently used as a catalyst (see Patent Literature 2), a method in which a gelled styrene-based polymer or a gelled polysiloxane-based polymer which has a phosphonium structure having a structure to coordinate a metal compound containing a specific metal atom is used as a catalyst (see Patent Literature 3), and the like are known. In these methods, it is required to recover and reuse the catalyst from the viewpoint of economic efficiency and environmental burden.
In the production of (meth) acrylates by a transesterification reaction, a method in which an organotin compound is used as a catalyst (see Patent Literature 1) is disclosed as a method for recovering and reusing a catalyst. However, in Patent Literature 1, it is required to further conduct the dehydration operation after the extraction operation by warm water is conducted plural times in order to recover the catalyst, and the step is complicated and the productivity remarkably decreases.
In addition, in Patent Literature 3, it is described that the catalyst can be separated through filtration after the reaction is completed. However, it is required to prepare a polymer having a special structure through a complicated step, and it is thus hard to say that this method is an economically advantageous production method.